Laser scanners

Laser scanners use a laser beam as the light source and typically employ either a reciprocating mirror or a rotating prism to scan the laser beam back and forth across the bar code. A photodiode is used to measure the intensity of the light reflected back from the bar code. The light emitted by the reader is rapidly varied in brightness with a data pattern and the photodiode receive circuitry is designed to detect only signals with the same modulated pattern.

Camera-based readers

Two-dimensional imaging scanners are the fourth and newest type of bar code reader. They use a camera and image processing techniques to decode the bar code.

Omni-directional bar code scanners

Omni-directional scanning uses "series of straight or curved scanning lines of varying directions that are projected at the symbol and one or more of them will be able to cross all of the symbol's bars and spaces, no matter what the orientation."

Omni-directional scanners almost all use a laser. Unlike the simpler single-line laser scanners, they produce a pattern of beams in varying orientations allowing them to read bar codes presented to it at different angles. Most of them use a single rotating polygonal mirror and an arrangement of several fixed mirrors to generate their complex scan patterns.